Thirty-six states potentially are ignoring the academic needs of large numbers of African American and Latino students, students from low-income families, English language learners, students with disabilities, and other groups of historically underserved students because the state accountability systems fail to capture these student subgroups. This fact sheet explains how states set the minimum number of students necessary to form these student subgroups, known as "n-size," and what that number means for monitoring and reporting the academic performance of historically underserved students under the Every Student Succeeds Act (ESSA).